Electrical switchgear assemblies, in particular medium-voltage switchgear assemblies, contain not only a circuit breaker, which is generally permanently installed, but also a disconnector, which can assume three positions: connected position, disconnected position and grounding position; that is to say it is in the form of a three-position switch. Furthermore, the three-position switch can be provided with a load-interrupter and/or circuit-breaker function.
In the connected position, a connection is produced to the live busbar, and in the grounding position, a connection is produced to ground. In the disconnected position, the moving contact piece of the disconnector is in a mid-position between the connected position and the grounding position.
Conventional three-position disconnectors are known in the form of in-line or knife switches. It is also known that an analogous functionality can also advantageously be provided by a “three-position vacuum switching chamber”.
In general, disconnectors are used as an autonomous appliance in the same gas area as the load-interrupter switch or circuit breaker, or in a separate gas area, particularly in the case of double busbar arrangements. The electrical part of these appliances is always a component of the gas area, and is connected by means of a gas-tight bushing to the drive, which is located inside and outside the gas area, and in medium-voltage applications, is normally in the form of a mechanical or magnetic drive.
As an autonomous appliance, a disconnector—if arranged in the same area as the load-interrupter switch or circuit breaker—requires a correspondingly large enclosure, or requires its own gas area if arranged separately. The latter in turn means additional passages between the different gas areas.
In both cases, additional complexity is required for material, assembly and testing. The dimensions of the switchgear assembly are correspondingly large, and this is disadvantageous.